United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
Cincinnati, Ohio 45268
Research and Development
EPA/600/S4-89/012 July 1989
4>EPA Project Summary
USE PA Method Study 37
SW-846 Method 3050
Acid Digestion of Sediments,
Sludges, and Soils
Kenneth Edgell
An interlaboratory collaborative
study was conducted on SW-846
Method 3050, "Acid Digestion of
Sediments, Sludges, and Soils," to
determine the overall and single-
analyst precision estimates for the
analyses of 23 elements in
sediments, sludges, and soils. SW-
846 Method 3050 includes quality
control, sample preparation, and
analysis of samples by Flame Atomic
Absorption (FLAA) and Graphite
Furnace Atomic Absorption (GFAA).
The study design was based upon
Youden's non-replicate plan for
collaborative tests of analytical
methods. Initially, 14 solid wastes
were collected, dried, homogenized,
and analyzed by Inductively Coupled
Plasma (ICP) for the 23 metals of
interest. Based upon these data,
seven solid wastes were selected
that contained naturally occurring
elements over a relatively wide
concentration range. Elements not
occurring naturally were added
(spiked) into each solid waste. In the
formal study by eight laboratories,
the solid wastes were digested with
nitric acid and hydrogen peroxide,
refluxed with nitric or hydrochloric
acid, and analyzed for 21 elements by
FLAA and for two elements, arsenic
and selenium, by GFAA. The results
were analyzed using USEPA com-
puter programs entitled "Inter-
laboratory Method Validation Study
(IMVS)." The computer programs
produced measures of overall and
single-analyst precision for the 21
elements analyzed by FLAA and for
the two elements analyzed by GFAA.
The study was conducted by The
Bionetics Corporation under the
direction of the Quality Assurance
Research Division, Environmental
Monitoring Systems Laboratory, Cin-
cinnati, OH (EMSL-Cincinnati) under
Contract No. 68-03-3254. Analytical
work was completed in August 1987.
The study report covers a period
from January 10, 1987, to February 5,
1988.
This Project Summary was
developed by EPA's Environmental
Monitoring Systems Laboratory, Cin-
cinnati, OH, to announce key findings
of the research project that is fully
documented in a separate report of
the same title (see Project Report
ordering information at back).
Introduction
The Hazardous Waste Management
facility permit regulations promulgated in
July 1982 (40 CFR 265) provide
performance standards for the monitoring
of ground waters, wastewaters, and solid
matrices at hazardous waste sites. To
facilitate these standards, chemical and
physical analyses are required to assess
the degree of contamination at and
around the area of the site. The manual:
7es/ Methods for Evaluating Solid Waste,
Physical and Chemical Methods, (SW-
846), November 1986, Third Edition,
provides a unified, up-to-date source of
information on sampling and analyses
related to compliance with Resource
Conservation and Recovery Act (RCRA)
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regulations. The success of these
pollution control activities, particularly
when legal action is involved, depends
upon the reliability of the data generated
by the laboratories; therefore, it is
important to evaluate the methods
through interlaboratory method validation
studies.
The Environmental Monitoring
Systems Laboratory, Cincinnati, OH,
(EMSL-Cincinnati) develops/selects ana-
lytical methods and provides quality
assurance (QA) support to agency
programs involving water and waste
regulations. In EMSL-Cincinnati, the
responsibility for providing QA support is
assigned to the Quality Assurance
Research Division (QARD). Its QA
program is designed to establish the
reliability and legal defensibility of water
and waste data collected by the Agency,
the state regulating authorities, the
private sector, and the commercial
laboratories performing compliance ana-
lyses. One of its QA activities is to
conduct interlaboratory method validation
studies to evaluate analytical methods
selected for the Agency's operating pro-
grams such as the Office of Solid Waste.
This report describes the
interlaboratory method validation study
for SW-846 Method 3050, "Acid Diges-
tion of Sediments, Sludges, and Soils."
The elements: aluminum, antimony, bar-
ium, beryllium, calcium, cadmium, chro-
mium, cobalt, copper, iron, lead,
magnesium,, manganese, molybdenum,
nickel, potassium, silver, sodium, thal-
lium, vanadium, and zinc were analyzed
by flame atomic absorption spectroscopy
(FLAA). Arsenic and selenium were
analyzed by graphite furnace atomic
absorption spectroscopy (GFAA). Origin-
ally, silver and antimony were included in
Method 3050 and therefore included in
this study. However, they were removed
from the September 1986 revision of the
method.
The primary objective of the study
was to characterize the behavior of
Method 3050 in terms of overall precision
and single-analyst precision. The study
was conducted with the cooperation of
eight participating laboratories under the
direction of the Quality Assurance Re-
search Division, EMSL-Cincinnati. As
primary contractor to QARD, The Bio-
netics Corporation was responsible for
the collection and characterization of the
solid matrices, preparation of user
instructions and report forms, distribution
of samples, and screening of the returned
data for gross errors. The raw data were
evaluated statistically by the QARD using
a series of computer programs entitled
"Interlaboratory Method Validation Stud-
ies" (IMVS). Upon review of the draft
report by EMSL-Cincinnati, The Bionetics
Corporation prepared the final report.
Description of Study
The study design was based upon
Youden's original non-replicate design for
collaborative evaluation of analytical
methods. In this design, samples are
prepared in pairs such that the analyte
concentrations of the pairs vary between
5-20% from the mean of the pairs. Seven
sample pairs, one for each solid matrix,
were prepared to cover the optimum
range of the method as specified in SW-
846 or in the concentration range
naturally occurring in the matrices.
Selection of Participating
Laboratories
Twenty-four commercial laboratories
responded to the abstract in the
Commerce Business Daily, inviting
participants for the method validation
study. Their technical proposals were
evaluated based upon laboratory exper-
ience and quality control practices.
Laboratories whose proposals were
acceptable were evaluated further in a
preaward performance evaluation study.
The participants selected for the formal
study were the eight laboratories with
acceptable proposals who performed
best in the preaward study.
Selection of Solid Waste
Matrices
Initially, 14 solid waste matrices were
screened for the 23 elements of interest
by ICP analyses and seven solid wastes
were selected that contained naturally
occurring elements over a relatively wide
concentration range. These were:
Solid
Waste Source
1 National Bureau of Standards River
Sediment, SRM-1645
2 US EPA, Hazardous Soil QC Sample
#1
3 Ethyl Corp., Electroplating Sludge
4 Marshall Space Flight Center (MSFC),
Electroplating Sludge
5 US EPA, Shale I QC Sample WP 386
6 Varland Metal Service Inc.,
Electroplating Sludge
7 EPA Supplied Electroplating Sludge
Aluminum, calcium, iron, magnesium,
manganese, potassium, and sodium were
present in all seven samples and did not
require fortification with spiking solution.
Cobalt, molybdenum, thallium, vanac
beryllium, cadmium, arsenic, selenium,
barium, silver, antimony, chromium,
copper, lead, nickel, and zinc did not
occur naturally or were at such low levels
in the solid wastes that fortification was
required.
Results and Discussion
The objective of this study was to
characterize the performance of SW-846
Method 3050 in terms of overall precision
and single-analyst precision for 23 trace
metals in sludges, soils, and sediments.
The IMVS computer programs were used
to summarize the raw data and compile
statistics for overall standard deviation,
overall percent relative standard
deviation, single-analyst standard
deviation, single-analyst percent relative
standard deviation, and mean recovery.
Antimony and silver, which are listed in
Table 1 are not included in the following
discussions because they are no longer
included in Method 3050.
The study was intended to answer two
major questions about method per-
formance:
(1) Does Method 3050 digestion
procedure work equally well on all
solid wastes studied? ^-N
(2) Do the matrix effects encounte
from any of the seven solid wasics
studied prevent establishment of a
linear relationship between precision
and mean recovery?
The following data treatment
decisions were made on the statistics
generated by the IMVS computer
programs:
1) Both overall and single-analyst pre-
cision regression equations were
recalculated after removal of atypical
solid waste data.
(2) Weighted linear regression equations
were not calculated with less than
five sets of acceptable solid waste
data. In these situations no
regression equation was reported,
and it was concluded that the data
for the element had a strong matrix
dependence. The reader is referred
to Appendix C, Statistical
Summaries, of the full report, for the
individual solid waste precision
statistics.
(3) For comparison purposes, a
concentration value of five times (5x)
the low concentration limit of the
range studied was used as the mean
recovery, in the regression
equations, to calculate %RSDs. ?"*
value is believed to be representa*.
of the reported data in this study.
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Rejection of Outliers
For the entire study, the IMVS
program rejected 75 data points (2.9%)
of the 2576 data points submitted. The
highest number of rejected points (10)
occurred for barium while no thallium or
beryllium data were rejected. Of the eight
laboratories participating in the study,
Laboratory 6 accounted for 25 of the 75
rejected data points.
Overall Precision
The IMVS computer programs calcu-
lated the overall precision for each of the
seven Youden concentration pairs for this
study. Utilizing another USEPA computer
program, REGRESS, weighted linear
regression equations were fitted to the
submitted data. These regression equa-
tions, presented in Table 1, regressed
overall precision (S) versus mean
recovery (X) for all seven Youden
concentration pairs (14 data points).
Several regression equations were
recalculated after deletion of solid waste
data which did not show a clear
relationship to the other solid waste data.
The deleted solid waste data are
^identified with each regression equation.
The mean %RSD for all FLAA
elements was 9.4%. Only two of these
elements, aluminum (22.4%) and potas-
sium (22.4%), had %RSDs greater than
15%, while fifteen elements had %RSDs
less that 10%. The naturally occurring
elements: aluminum, calcium, iron,
magnesium, manganese, potassium and
sodium, which did not require fortification,
had a mean %RSD of 11.8%. Cobalt,
molybdenum, thallium, and vanadium,
which required spiking of all seven solid
wastes, had a mean %RSD of 8.4%.
Beryllium, cadmium, chromium, copper,
lead, nickel, and zinc which were
evaluated with a combination of spiked
and unspiked solid wastes had a mean
%RSD of 7.4%. Based on the mean
%RSDs for these three groups, the
overall precision obtained for all elements
was very similar whether naturally
present or spiked into the solid matrices.
The %RSD for the GFAA elements,
arsenic and selenium, were 19.7% and
29.6%, respectively.
Barium regression equations are not
presented in Table 1 because the
precision data for each of the seven solid
wastes were variable with no apparent
^relationship to mean recoveries.
Precipitation reactions forming barium
sulfate are suspected but have not been
confirmed.
Single-Analyst Precision
The IMVS computer programs
calculated the single-analyst precision
(SR) for each of the seven Youden
concentration pairs for this study. The
seven results for each element were
reduced to a single equation by weighted
linear regression analysis. These
regression equations, presented in Table
1, regressed single-analyst precision (SR)
versus mean recovery (X) and can be
used to estimate the percent relative
single-analyst standard deviation (%RSD-
SR) at any concentration level in the
range studied.
The mean %RSD-SR for the FLAA
elements was 5.4% and ranged from
cobalt (4.2%) to aluminum (8.6%). The
ratio of the mean overall precision,
%RSD, to the mean single-analyst preci-
sion, %RSD-SR, was 1.7:1. The naturally
occurring elements: aluminum, calcium,
iron, magnesium, manganese, potassium
and sodium had a mean %RSD-SR of
5.8%. Cobalt, molybdenum, thallium and
vanadium which required spiking of all
seven solid wastes, had a mean %RSD-
SR of 5.1%. Beryllium, cadmium, chro-
mium, copper, lead, nickel, and zinc were
analyzed from a combination of spiked
and unspiked solid wastes and had a
mean %RSD-SR of 5.2%. Based on the
mean %RSD-SRs for these three groups,
the within-laboratory precision obtained
for all elements, whether naturally
present or spiked into the solid matrices,
was very similar.
The GFAA elements, arsenic and
selenium, had %RSD-SRs of 11.4% and
23.0% respectively and were the only
elements with %RSD-SRs above 10%.
Conclusions and
Recommendations
SW-846 Method 3050 is recom-
mended for the analyses of aluminum,
barium, beryllium, cadmium, calcium,
chromium, cobalt, copper, iron, lead,
magnesium, manganese, molybdenum,
nickel, potassium, sodium, thallium, vana-
dium, and zinc by flame atomic
absorption (FLAA) and for the analyses of
arsenic and selenium by graphite furnace
atomic absorption (GFAA).
The linear regression equations
obtained from this study and presented in
Table 1 can be used to predict the overall
and single-analyst precision of Method
3050 for these elements over the
concentration range studied
The barium precision data obtained
from this study were variable with no
apparent relationship to mean recovery.
Reactions, perhaps involving barium
sulfate as a precipitate, are theorized.
Barium data from the Method 3050
digestion procedure should be evaluated
relative to presence of sulfur or sulfur
oxides in wastes tested.
Originally, silver and antimony were
included in Method 3050 but were
removed from the September 1986
revision of the method. They were,
however, included in this study but are
not recommended for analyses by
Method 3050.
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Table 1. Regression Equations for Overall (S) and Single-analyst (SR) Precision for SW-846 Method 3050
Data Set Corrected for Waste
Element (Cone Range in ng/gj Regression Equation3 Waste No. Deleted11 No.c
Aluminum (715-18700)
Antimony (63-1700)
Beryllium (5.5-231)
Cadmium (5.6-154)
Calcium (11900-185000)
Chromium (67-97700)
Cobalt (91-624)
Copper (66-25800)
Iron (16900-123400)
Lead (715-20800)
Magnesium (2050-50700)
Manganese (287-1100)
Molybdenum (180-5600)
Nickel (22-75000)
Potassium (448-4100)
Sodium (227-105700)
Thallium (129-2400)
Vanadium (334-7420)
Zinc (93-188900)
Arsenic" (21-616)
Selenium* (3.98-105)
Barium* (123-11630)
Silver* (37-344)
S=0.210X + 51.0
SR=0.0742X + 41.2
S=0.145X + 10.58
SR=0.0310X + 16.35
S=0.0676X + 0.37
SR=0.0411X * 0.26
S=0.0437X + 0.78
SR=0.0446X + 0.41
S=0.0893X- 66
SR=0.0662X -881
S=0.0923X + 0.73
SR=0.0564X + 0.66
S=0.0525X + 7.22
SR=0.0428X -0.40
S=0.0636X + 0.0
SR=0.0460X + 2.0
S=0.0522X + 693
SR=0.0364X + 162
S=0.0607X - 17.4
SR= 0.0292 X + 4.3
S=0.0572X + 106
SR = 0.0408X + 26
S=0.0840X -3.0
SR = 0.061 8X- 6.2
S=0.0739X -3.5
SR=0.0936X-10.8
4 A 43
S=0.0678X
Sfl=0.0437X
6.44
5.64
S=0.796X + 61.8
SR=0.0739X + 16.1
S=0.0646X + 26.4
SR=0.0481X + 8.4
S=0.0559X + 7.5
SR=0.0213X + 4.3
S=0.133X -4.2
SR=0.0437X -i- 13.6
S=0.0832X + 1.10
SR=0.0639X + 1.33
S=0.188X + 0.98
SR=0.0857X + 2.95
S=0.192X * 2.06
Sfl=0.787X + 0.85
No equation developed. See App. C
in main report for individual statistics.
No equation developed. See App. C
in main report for individual statistics.
1,7
1,7
6,7
6,7
7
7
6
6
6
6
2,5
2,5
1A, 1B, 2B
5B
7B
All data sets corrected except
5A.5B
2A, 28, 78
6B
5A, 6A, 7A,7B
All data sets corrected
a Weighted least squares technique.
b Indicates the waste deleted to arrive at the regression equation presented.
c Solid waste data set that was corrected for errant data points. See Section 5, Results and Discussion, for further details in
main report.
d Analyzed by graphite furnace atomic absorption (GFAA). All other analyses by flame atomic absorption (FLAA).
e The individual data sets were too variable to fit a linear relationship; thus, no equations were developed.
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Kenneth Edgell is with The Bionetics Corporation, Cincinnati, OH 45246
Edward L Berg is the EPA Project Officer (see below).
The complete report, entitled "USEPA Method Study 37, SW-846 Method 3050
Acid Digestion of Sediments, Sludges, and Soils," (Order No. PB 89-181
9521 AS; Cost: $21.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
EPA/600/S4-89/012
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